1. Field of the invention
The present invention relates to sound reproducing systems for producing tremolo effects, and, more particularly, to novel tremolo effect producing systems most suitable for use with electronic musical instruments.
2. Description of the Prior Art
As the conventional sound reproducing system for producing a tremolo effect on sounds as they are generated by an electronic musical instrument, there is known the type having a rotational disc located in front of a loudspeaker or speakers to thereby provide a tremolo effect, as disclosed in, for example, Japanese Utility Model Publication No. 22436/1965 and U.S. Pat. No. 3,204,722.
Said Utility Model Publication, as shown in FIG. 1, discloses a tremolo effect producing apparatus comprising a motor 1, a rotational shaft 2 operatively connected with the motor, an acoustic reflecting plate 3 of which the center is supported by the end of the shaft so as to be rotatable in any plane involving the shaft, a bearing 4 slidably engaged with the shaft 2, a connecting lever 5 connecting the bearing 4 with the side portion of the relfecting plate 3, and a loudspeaker 6 in front of which is located the reflecting plate 3 so as to face it, whereby the sounds from the speaker provides a tremolo effect through the reflecting plate as the plate is rotated with respect to the direction of the shaft, namely, axially of the loudspeaker.
Said U.S. patent, as shown in FIGS. 2 and 3, discloses another system for generating a tremolo effect on the sound waves from speakers including a sound reproducing speaker enclosing cabinet, a vertically disposed speaker supporting panel spaced inwardly from an open side of the cabinet, a plurality of sound reproducing speakers 6 mounted on the panel, a rotating disc 7A spaced from and operating in a plane parallel with the speaker supporting panel and having openings corresponding in diameters with the diameters of the diaphragms of the speakers or a rotating plate 7B having cutouts and a motor for rotating the disc or the plate at a required revolution speed.
Other known device of the type in which a plurality of speakers are rotated in a plane to produce a tremolo effect is referred to in the following two U.S. patents. That is, U.S. Pat. No. 3,100,024, as shown in FIGS. 4 and 5, discloses an apparatus for producing vibrato or tremolo effects, comprising a motor 1, a drum 8 arranged on the inside of a peripheral wall on which a plurality of speakers 6 are revolvably mounted for rotation about an axis, the drum being operatively connected with the motor through a belt so as to be rotated, and slip rings R through which low frequency currents are supplied to the respective speakers, whereby the sounds from the speakers are given vibrato or tremolo effects as the speakers are horizontally rotated in the same plane with that of rotation of the drum driven by the motor.
As shown in FIG. 6, U.S. Pat. No. 3,084,585 indicates an acoustic modulator comprising a speaker mounting disc 9 having circumferentially disposed plural speakers 6 which may be rotated about a horizontal axis, namely, circumferentially by means of a suitable motor MA and may be rotated about a vertical axis of a vertical standard lC, namely, perpendicularly to the vertically diametric direction of the disc, by means of another motor MB, to produce a Doppler effect and a tremolo effect.
However, these known tremolo effect producing systems have the following disadvantages.
First, the known tremolo effect producing apparatus are inconveniently bulky, occupying a large space, include complicated mechanisms and cannot effectively produce a tremolo effect when sound is reproduced by means of headphones in an electronic musical instrument. Furthermore, when incorporated in an electronic musical instrument, such an apparatus generally requires a fixed loudspeaker for sound reproduction having a non-tremolo effect, as well as a rotating loudspeaker for providing a tremolo effect, and also separate power amplifiers therefor.
Accordingly, such apparatus not only tend to be very expensive but also cannot radiate tremolo and non-tremolo sounds from the same speaker, resulting in the lack of naturalness of sound in the performance of the electronic musical instrument.